[OriginTransition] Make the library resilient to view being detached in

the middle of transition.

1. In ViewUIComponent, gracefully handle the case when view is detached
   from the window.
2. Cancelling an origin transition session will also cancel the running
   remote transition.

Flag: EXEMPTED - bug fix
Test: manual test
Change-Id: I72f553c97e62101d32e41a601b355d125e83eb9c